document which settings macros are allowed to change in between world join and timer start

[tildejustin]

believed to be fov, rd, ed, gui scale, difficulty, and f1, could be more. this is seemingly a rule for which the details have been lost to time (I didn't even know it was a limited list) so we probably have to redefine the list only with current known instances (from the original thread, it seems like contaria just chose which settings he thought were ok and mods didn't clarify any ideology at the time https://discord.com/channels/83066801105145856/966388288460034048/982693820871376916). if anyone knows of more historical allowances please do share (old 1.16 settings change macros could be useful).

[tildejustin]

counterpoint: all gui settings, no hotkey settings except f1? I'm not sure what I was thinking when I wrote this. taking off the milestone for v7 and probably eligible for closing I just want to make sure the basis for and extent of these rules is well-documented first because standardsettings relies on them.